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4a8412d430
@colincross identified gcd does not have a single case whose answer is not 0, 1, or the smaller of the two inputs.
242 lines
7.6 KiB
C++
242 lines
7.6 KiB
C++
//===----------------------------------------------------------------------===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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//
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// UNSUPPORTED: c++03, c++11, c++14
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// <numeric>
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// template<class _M, class _N>
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// constexpr common_type_t<_M,_N> gcd(_M __m, _N __n)
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#include <numeric>
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#include <cassert>
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#include <climits>
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#include <cstdint>
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#include <limits>
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#include <random>
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#include <type_traits>
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#include "test_macros.h"
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constexpr struct {
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int x;
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int y;
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int expect;
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} Cases[] = {
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{0, 0, 0},
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{1, 0, 1},
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{0, 1, 1},
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{1, 1, 1},
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{2, 3, 1},
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{2, 4, 2},
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{11, 9, 1},
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{36, 17, 1},
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{36, 18, 18},
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{25, 30, 5},
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{24, 16, 8},
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{128, 100, 4}};
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template <typename Input1, typename Input2, typename Output>
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constexpr bool test0(int in1, int in2, int out)
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{
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auto value1 = static_cast<Input1>(in1);
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auto value2 = static_cast<Input2>(in2);
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static_assert(std::is_same_v<Output, decltype(std::gcd(value1, value2))>, "");
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static_assert(std::is_same_v<Output, decltype(std::gcd(value2, value1))>, "");
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assert(static_cast<Output>(out) == std::gcd(value1, value2));
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return true;
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}
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template <typename T>
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T basic_gcd_(T m, T n) {
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return n == 0 ? m : basic_gcd_<T>(n, m % n);
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}
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template <typename T>
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T basic_gcd(T m, T n) {
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using Tp = std::make_unsigned_t<T>;
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if constexpr (std::is_signed_v<T>) {
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if (m < 0 && m != std::numeric_limits<T>::min())
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m = -m;
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if (n < 0 && n != std::numeric_limits<T>::min())
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n = -n;
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}
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return basic_gcd_(static_cast<Tp>(m), static_cast<Tp>(n));
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}
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template <typename Input>
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void do_fuzzy_tests() {
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std::mt19937 gen(1938);
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using DistIntType = std::conditional_t<sizeof(Input) == 1, int, Input>; // See N4981 [rand.req.genl]/1.5
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constexpr Input max_input = std::numeric_limits<Input>::max();
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std::uniform_int_distribution<DistIntType> distrib(0, max_input);
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constexpr int nb_rounds = 10000;
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for (int i = 0; i < nb_rounds; ++i) {
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Input n = static_cast<Input>(distrib(gen));
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Input m = static_cast<Input>(distrib(gen));
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assert(std::gcd(n, m) == basic_gcd(n, m));
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}
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}
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template <typename Input>
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void do_limit_tests() {
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Input inputs[] = {
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// The behavior of std::gcd is undefined if the absolute value of one of its
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// operand is not representable in the result type.
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std::numeric_limits<Input>::min() + (std::is_signed<Input>::value ? 3 : 0),
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std::numeric_limits<Input>::min() + 1,
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std::numeric_limits<Input>::min() + 2,
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std::numeric_limits<Input>::max(),
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std::numeric_limits<Input>::max() - 1,
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std::numeric_limits<Input>::max() - 2,
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0,
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1,
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2,
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3,
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4,
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5,
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6,
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7,
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8,
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9,
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10,
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(Input)-1,
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(Input)-2,
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(Input)-3,
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(Input)-4,
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(Input)-5,
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(Input)-6,
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(Input)-7,
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(Input)-8,
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(Input)-9,
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(Input)-10,
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};
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for (auto n : inputs) {
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for (auto m : inputs) {
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assert(std::gcd(n, m) == basic_gcd(n, m));
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}
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}
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}
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template <typename Input1, typename Input2 = Input1>
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constexpr bool do_test(int = 0)
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{
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using S1 = std::make_signed_t<Input1>;
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using S2 = std::make_signed_t<Input2>;
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using U1 = std::make_unsigned_t<Input1>;
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using U2 = std::make_unsigned_t<Input2>;
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bool accumulate = true;
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for (auto TC : Cases) {
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{ // Test with two signed types
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using Output = std::common_type_t<S1, S2>;
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accumulate &= test0<S1, S2, Output>(TC.x, TC.y, TC.expect);
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accumulate &= test0<S1, S2, Output>(-TC.x, TC.y, TC.expect);
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accumulate &= test0<S1, S2, Output>(TC.x, -TC.y, TC.expect);
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accumulate &= test0<S1, S2, Output>(-TC.x, -TC.y, TC.expect);
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accumulate &= test0<S2, S1, Output>(TC.x, TC.y, TC.expect);
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accumulate &= test0<S2, S1, Output>(-TC.x, TC.y, TC.expect);
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accumulate &= test0<S2, S1, Output>(TC.x, -TC.y, TC.expect);
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accumulate &= test0<S2, S1, Output>(-TC.x, -TC.y, TC.expect);
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}
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{ // test with two unsigned types
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using Output = std::common_type_t<U1, U2>;
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accumulate &= test0<U1, U2, Output>(TC.x, TC.y, TC.expect);
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accumulate &= test0<U2, U1, Output>(TC.x, TC.y, TC.expect);
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}
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{ // Test with mixed signs
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using Output = std::common_type_t<S1, U2>;
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accumulate &= test0<S1, U2, Output>(TC.x, TC.y, TC.expect);
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accumulate &= test0<U2, S1, Output>(TC.x, TC.y, TC.expect);
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accumulate &= test0<S1, U2, Output>(-TC.x, TC.y, TC.expect);
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accumulate &= test0<U2, S1, Output>(TC.x, -TC.y, TC.expect);
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}
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{ // Test with mixed signs
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using Output = std::common_type_t<S2, U1>;
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accumulate &= test0<S2, U1, Output>(TC.x, TC.y, TC.expect);
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accumulate &= test0<U1, S2, Output>(TC.x, TC.y, TC.expect);
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accumulate &= test0<S2, U1, Output>(-TC.x, TC.y, TC.expect);
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accumulate &= test0<U1, S2, Output>(TC.x, -TC.y, TC.expect);
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}
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}
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return accumulate;
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}
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int main(int argc, char**)
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{
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int non_cce = argc; // a value that can't possibly be constexpr
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static_assert(do_test<signed char>(), "");
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static_assert(do_test<short>(), "");
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static_assert(do_test<int>(), "");
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static_assert(do_test<long>(), "");
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static_assert(do_test<long long>(), "");
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assert(do_test<signed char>(non_cce));
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assert(do_test<short>(non_cce));
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assert(do_test<int>(non_cce));
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assert(do_test<long>(non_cce));
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assert(do_test<long long>(non_cce));
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static_assert(do_test<std::int8_t>(), "");
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static_assert(do_test<std::int16_t>(), "");
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static_assert(do_test<std::int32_t>(), "");
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static_assert(do_test<std::int64_t>(), "");
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assert(do_test<std::int8_t>(non_cce));
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assert(do_test<std::int16_t>(non_cce));
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assert(do_test<std::int32_t>(non_cce));
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assert(do_test<std::int64_t>(non_cce));
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static_assert(do_test<signed char, int>(), "");
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static_assert(do_test<int, signed char>(), "");
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static_assert(do_test<short, int>(), "");
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static_assert(do_test<int, short>(), "");
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static_assert(do_test<int, long>(), "");
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static_assert(do_test<long, int>(), "");
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static_assert(do_test<int, long long>(), "");
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static_assert(do_test<long long, int>(), "");
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assert((do_test<signed char, int>(non_cce)));
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assert((do_test<int, signed char>(non_cce)));
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assert((do_test<short, int>(non_cce)));
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assert((do_test<int, short>(non_cce)));
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assert((do_test<int, long>(non_cce)));
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assert((do_test<long, int>(non_cce)));
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assert((do_test<int, long long>(non_cce)));
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assert((do_test<long long, int>(non_cce)));
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// LWG#2837
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{
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auto res = std::gcd(static_cast<std::int64_t>(1234), INT32_MIN);
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static_assert(std::is_same_v<decltype(res), std::int64_t>, "");
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assert(res == 2);
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}
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do_fuzzy_tests<std::int8_t>();
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do_fuzzy_tests<std::int16_t>();
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do_fuzzy_tests<std::int32_t>();
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do_fuzzy_tests<std::int64_t>();
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do_fuzzy_tests<std::uint8_t>();
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do_fuzzy_tests<std::uint16_t>();
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do_fuzzy_tests<std::uint32_t>();
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do_fuzzy_tests<std::uint64_t>();
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do_limit_tests<std::int8_t>();
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do_limit_tests<std::int16_t>();
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do_limit_tests<std::int32_t>();
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do_limit_tests<std::int64_t>();
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do_limit_tests<std::uint8_t>();
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do_limit_tests<std::uint16_t>();
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do_limit_tests<std::uint32_t>();
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do_limit_tests<std::uint64_t>();
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return 0;
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}
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